For those who don't care to be held hostage by the journalist as he forces you through a long winded narrative: gold and silver nano particles are embedded into the glass

This has been known for a long long time too (decades+), its not a recent discovery. Journalism is just marketing at this point.

Now if only we knew how the cage cups (of which the Licurgus Cup is actually an example) were made...

> This has been known for a long long time too (decades+), its not a recent discovery.

We've known what caused the effect for a long time. We did _not_ know how they achieved the nanoparticle mix and size in the glass, last I checked. This story is about someone actually taking the basic idea and making a real object.

I wonder if the more accurate title might be: Scientists Discover How Ancient Romas Made Color-Changing Glass. Meaning that I've seen many examples of glass that appears different colors under different circumstances, but apparently none that worked the way this cup does.

The ancient artefact described also featured in a Jonathon Blow lecture, as an example of an engineering skill we lost for 1600 years: https://youtu.be/ZSRHeXYDLko?t=402

Perhaps he saw it on hn that time https://news.ycombinator.com/item?id=19781608

The Romans appreciated much more the jewels with variable colors than those with fixed colors.

Those among opals and pearls that exhibited a very strong play of colors, due to diffraction, were valued far above the gems with fixed color, like emeralds and rubies.

Thus it is likely that this kind of glass, with different colors in transmitted and reflected light, was very expensive, so it is not surprising that in TFA a letter of one of the Roman emperors is cited, where he mentions receiving such cups as a gift, because they certainly would have been considered a gift worthy of an emperor.

Note that rubies are also color changing (thermochromatic)! The absorption band gap of ruby (well, really the Cr d-shell band) expands to longer wave lengths at high temp and contracts at low temperatures so that it is light orange ~77K or -200C and turns black (IR) ~400C.

Huh? I remember my grandma having these magnets (usually a boat or the like) in the fridge that would change color with the weather, so it would “tell you” if it was going to rain or not.

Is this that?